The "e" in COe represents the word equivalent and refers to the sum of unburned molecules such as carbon monoxide (CO), methane (CH4) or hydrogen (H2) in the process gas.

This group of unburned molecules form, apart from oxygen molecules, the only gases in which by means of InSitu measurement, the quality of combustion can be analysed. High COe values are an indicator for an inefficient, climate harmful and plant hostile process control.

From a safety point of view, monitoring the COe values can also be used for recognition of smouldering fires.